1. Field of the Invention
The invention relates to a gamma voltage generator, and more particularly to a gamma voltage generator utilizing only a resistor string.
2. Description of the Related Art
Liquid crystal displays (LCDs) are widely used due to their favorable advantages, which include thin profile, low weight, and low radiation,. A display array of one LCD comprises a plurality of pixel units. Each pixel unit comprises a red sub-pixel, a green sub-pixel, and a blue sub-pixel. The brightness of each sub-pixel is determined according to its gamma voltage.
FIG. 1 is a schematic diagram of a conventional gamma voltage generator. Conventional gamma voltage generator 10 comprises setting units 121˜123 and gamma circuits 141˜143. Each of the gamma circuits 141˜143 is a resistor string.
Gamma circuit 141 generates point voltages VR1˜VRn for controlling brightness of red sub-pixels (not shown) when setting unit 121 provides a setting signal SS121 to the gamma circuit 141.
Gamma circuit 142 generates point voltages VG1˜VGn for controlling brightness of green sub-pixels (not shown) when the setting unit 122 provides a setting signal SS122 to the gamma circuit 142.
Gamma circuit 143 generates point voltages VB1˜VBn for controlling brightness of blue sub-pixels (not shown) when the setting unit 123 provides a setting signal SS123 to the gamma circuit 143.
To display different levels of brightness, the sum of the resistors is increased. When the sum of the resistors of gamma circuit 141 is increased, the sum of the resistors of gamma circuits 142 and 143 must be increased, thus, the cost of gamma circuits is increased and usable space is reduced.